The present invention relates to an undercarriage frame structure for an excavator or power shovel that provides proper support for a bearing and ring gear of an excavator upper structure without machining the frame, resulting in reduced manufacturing costs. The frame is used for supporting additional components for mounting the tracks that propel the excavator, and auxiliary equipment such as a backfill blade.
In the prior art, mini excavators or small power shovels are widely used. These are track propelled vehicles that have an undercarriage mounting the track and accessory items, and including a frame with a horizontal surface on which a bearing and ring gear that supports a rotatable turntable plate is mounted. The turntable mounts a cab and operator's platform, as well as the excavator bucket. The existing undercarriage frame that mount the bearing and a ring gear typically is a very thick or heavy plate that has a machined surface on which the bearing support is mounted, in order to obtain a surface that is flat and perpendicular to the vertical axis of rotation. The plate is large and heavy, making it difficult to handle and time consuming to machine, which increases the manufacturing costs. Since the bearing support ring is quite heavy as well, any portion of the surface on the heavy plate that is out of true will cause the bearing to be inaccurately located.
Various types of frames have been advanced, but the need for machining has been a source of extra cost for years.